Laterally diffused metal oxide semiconductor device and method for manufacturing the same

ABSTRACT

A laterally diffused metal oxide semiconductor device can include: a base layer; a source region and a drain region located in the base layer; a first dielectric layer located on a top surface of the base layer and adjacent to the source region; a voltage withstanding layer located on the top surface of the base layer and located between the first dielectric layer and the drain region; a first conductor at least partially located on the first dielectric layer; a second conductor at least partially located on the voltage withstanding layer; and a source electrode electrically connected to the source region, where the first and second conductors are spatially isolated, and the source electrode at least covers a space between the first and second conductors.

RELATED APPLICATIONS

This application is a continuation of the following application, U.S.patent application Ser. No. 16/412,587, filed on May 15, 2019, and whichis hereby incorporated by reference as if it is set forth in full inthis specification, and which also claims the benefit of Chinese PatentApplication No. 201810515185.8, filed on May 25, 2018, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to semiconductor devices, andmore particularly to laterally diffused metal oxide semiconductordevices and associated methods.

BACKGROUND

Voltage regulators, such as DC-to-DC voltage converters, are used toprovide stable voltage sources for various electronic systems. EfficientDC-to-DC converters are particularly useful for battery management inlow power devices (e.g., laptop notebooks, cellular phones, etc.). Aswitching voltage regulator can generate an output voltage by convertingan input DC voltage into a high frequency voltage, and then filteringthe high frequency input voltage to generate the output DC voltage. Forexample, the switching regulator can include a switch for alternatelycoupling and decoupling an input DC voltage source (e.g., a battery) toa load (e.g., an integrated circuit [IC], a light-emitting diode [LED],etc.). An output filter, can include an inductor and a capacitor, andmay be coupled between the input voltage source and the load to filterthe output of the switch, and thus provide the output DC voltage. Acontroller (e.g., a pulse-width modulator, a pulse frequency modulator,etc.) can control the switch to maintain a substantially constant outputDC voltage. Lateral double-diffused metal oxide semiconductor (LDMOS)transistors may be utilized in switching regulators due to theirperformance in terms of a tradeoff between their specific on-resistance(R_(dson)) and drain-to-source breakdown voltage (BV_(d_s)).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an example laterally diffused metaloxide semiconductor device.

FIG. 2 is a cross-sectional view of a first example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 3 is a cross-sectional view of a second example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 4 is a cross-sectional view of a third example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 5 is a cross-sectional view of a fourth example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 6 is a cross-sectional view of a fifth example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 7 is a cross-sectional view of a sixth example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

FIG. 8 is a cross-sectional view of a seventh example laterally diffusedmetal oxide semiconductor device, in accordance with embodiments of thepresent invention.

DETAILED DESCRIPTION

Reference may now be made in detail to particular embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention may be described in conjunction with thepreferred embodiments, it may be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents that may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it may be readilyapparent to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, processes, components, structures, and circuitshave not been described in detail so as not to unnecessarily obscureaspects of the present invention.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing may involve the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer may contain active and passive electrical components, whichare electrically connected to form functional electrical circuits.Active electrical components, such as transistors and diodes, have theability to control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, resistors, and transformers,create a relationship between voltage and current necessary to performelectrical circuit functions.

Passive and active components can be formed over the surface of thesemiconductor wafer by a series of process steps including doping,deposition, photolithography, etching, and planarization. Dopingintroduces impurities into the semiconductor material by techniques suchas ion implantation or thermal diffusion. The doping process modifiesthe electrical conductivity of semiconductor material in active devices,transforming the semiconductor material into an insulator, conductor, ordynamically changing the semiconductor material conductivity in responseto an electric field or base current. Transistors contain regions ofvarying types and degrees of doping arranged as necessary to enable thetransistor to promote or restrict the flow of electrical current uponthe application of the electric field or base current.

Active and passive components are formed by layers of materials withdifferent electrical properties. The layers can be formed by a varietyof deposition techniques determined in part by the type of materialbeing deposited. For example, thin film deposition may involve chemicalvapor deposition (CVD), physical vapor deposition (PVD), electrolyticplating, and electroless plating processes. Each layer is generallypatterned to form portions of active components, passive components, orelectrical connections between components.

The layers can be patterned using photolithography, which involves thedeposition of light sensitive material, e.g., photoresist, over thelayer to be patterned. A pattern is transferred from a photomask to thephotoresist using light. The portion of the photoresist patternsubjected to light is removed using a solvent, exposing portions of theunderlying layer to be patterned. The remainder of the photoresist maybe removed, leaving behind a patterned layer. Alternatively, some typesof materials can be patterned by directly depositing the material intothe areas or voids formed by a previous deposition/etch process usingtechniques such as electroless and electrolytic plating.

Depositing a thin film of material over an existing pattern canexaggerate the underlying pattern and create a non-uniformly flatsurface. A uniformly flat surface may be used to produce smaller andmore densely packed active and passive components. Planarization can beused to remove material from the surface of the wafer and produce auniformly flat surface. Planarization can involve polishing the surfaceof the wafer with a polishing pad. An abrasive material and corrosivechemical are added to the surface of the wafer during polishing. Thecombined mechanical action of the abrasive and corrosive action of thechemical removes any irregular topography, resulting in a uniformly flatsurface.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual die and then packaging the die for structuralsupport and environmental isolation. To singulate the die, the wafer isscored and broken along non-functional regions of the wafer called sawstreets or scribes. The wafer may be singulated using a laser cuttingtool or saw blade. After singulation, the individual die are mounted toa package substrate that includes pins or contact pads forinterconnection with other system components. Contact pads formed overthe semiconductor die can then be connected to contact pads within thepackage. The electrical connections can be made with solder bumps, studbumps, conductive paste, or wire bonds, as a few examples. Anencapsulant or other molding material may be deposited over the packageto provide physical support and electrical isolation. The finishedpackage can then be inserted into an electrical system and thefunctionality of the semiconductor device is made available to the othersystem components.

Referring now to FIG. 1 , shown is a cross-sectional view of an examplelaterally diffused metal oxide semiconductor device. In this particularexample, semiconductor device 100 can include P-type substrate PSUB,high voltage N-type well region HVNW in P-type substrate PSUB, andP-type body region Pbody and N-type drift region N-drift in high voltageN-type well region HVNW. A source region N+ and a drain region N+ canrespectively be formed in P-type body region Pbody and N-type driftregion N-drift. A body contact region P+ may also be formed in theP-type body region Pbody and be arranged in contact with the sourceregion N+. A gate dielectric layer can be arranged on a surface ofsemiconductor device 100 and adjacent to the source region. Thick oxidelayer Oxide between the gate dielectric layer and the drain region canbe arranged on the surface of semiconductor device 100. A gate conductorpoly can cover the gate dielectric layer and extends to the thick oxidelayer Oxide.

In semiconductor device 100, gate conductor may extend from the gatedielectric layer to thick oxide layer Oxide, and the entire conductorlayer Poly can act as a gate conductor, which can receive a controlvoltage controlling the turn-on/off of semiconductor device 100 throughthe gate electrode. Therefore, when semiconductor device 100 is in theoff state, the potential on thick oxide layer Oxide may not assist indepleting the N-type drift region N-drift, and the high-voltagebreakdown performance of the device may not be maintained. Further, thegate electrode can extend above the N-type drift region N-drift, and theoverlap between the gate region and the drain region may be relativelylarge, such that the gate charge Qgd is relatively large, and the highfrequency application of semiconductor device 100 is accordinglylimited.

In one embodiment, a laterally diffused metal oxide semiconductor devicecan include: (i) a base layer; (ii) a source region and a drain regionlocated in the base layer; (iii) a first dielectric layer located on atop surface of the base layer and adjacent to the source region; (iv) avoltage withstanding layer located on the top surface of the base layerand located between the first dielectric layer and the drain region; (v)a first conductor at least partially located on the first dielectriclayer; (vi) a second conductor at least partially located on the voltagewithstanding layer; and (vii) a source electrode electrically connectedto the source region, where the first and second conductors arespatially isolated, and the source electrode at least covers a spacebetween the first and second conductors.

Referring now to FIG. 2 , shown is a cross-sectional view of a firstexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. Semiconductordevice 200 can include a base layer, a source region, a drain region, afirst dielectric layer, and a voltage withstanding layer. The sourceregion and the drain region can be located in the base layer, the firstdielectric layer may be located on the top surface of the base layer andadjacent to the source region, and the voltage withstanding layer can belocated on the top surface of the base layer and between the firstdielectric layer and the drain region. Semiconductor device 200 can alsoinclude a first conductor on the first dielectric layer, a secondconductor on the voltage withstanding layer, and a source electrodeelectrically connected to the source region. The first and secondconductors can be spatially isolated, and the source electrode may coverat least a space between the first and second conductors. The spatialisolation is that the first and second conductors are not in contactwith each other in space, and are separated from each other.

In semiconductor device 200, the source region and the drain region areboth N-type doped N+ regions. In other examples, the source region andthe drain region may be P-type doped P+ regions. The base layer caninclude a P-type doped substrate PSUB and an N-type high voltage wellregion HVNW located in the P-type substrate PSUB. In other examples, thebase layer may be composed only of a semiconductor substrate. The firstdielectric layer may serve as a gate dielectric layer, and the firstconductor can be a gate conductor for electrically connecting the gateelectrode Gate. The first dielectric layer may be an oxide layer (e.g.,a SiO2 layer), and the first conductor may be a polysilicon layer Poly1covering the first dielectric layer. The voltage withstanding layer maybe a local oxidation of silicon (LOCOS) dielectric layer (e.g., thickoxide layer Oxide), and thick oxide layer Oxide may be a bird's beakshape, where the thickness of the voltage withstanding layer is greaterthan the thickness of the first dielectric layer. The second conductormay be polysilicon Poly2 on the voltage withstanding layer.

The second conductor can be electrically connected to field plateelectrode Plate1. Field plate electrode Plate1 can connect to the samepotential as source electrode Source. That is, field plate electrodePlate1 may be electrically connected to source electrode Source, orfield plate electrode Plate1 may be connected to other potentialsseparately, and field plate electrode Plate1 can connect to differentpotential from gate electrode Gate. Since field plate electrode Plate1and gate electrode Gate are connected to different potentials, when thepotential connected to gate electrode Gate causes semiconductor device200 to be in an off state, field plate electrode Plate1 can still assistin depleting the drift region by receiving a certain potential, in orderto maintain the high voltage withstanding of semiconductor device 200.In addition, since the first conductor is fully located on the firstdielectric layer, such that an overlapping portion between the firstconductor and the drain portion (e.g., a region where the drain regionis located) becomes relatively small, gate charge Qgd can be greatlyreduced, such that semiconductor device 200 can be suitable in a highfrequency field.

Source electrode Source can electrically be connected to the sourceregion and may extend at least to above the second conductor (e.g.,polysilicon Poly2) such that the first dielectric layer and/or thickoxide layer Oxide located between the first and second conductors arecovered by the source electrode. That is, the space between the firstand second conductors can be covered by the source electrode Source,which may not mean that source electrode Source is directly in contactwith first dielectric layer and/or the voltage-withstanding layer, butrather is non-contact covering (e.g., source electrode Source is locatedabove the first dielectric layer and/or the voltage-withstanding layer).The electric field at the disconnected position of the first and secondconductors may drop, and in semiconductor device 200, the disconnectedposition can be covered by source electrode Source without contact toavoid the dropping phenomenon, thereby improving the voltagewithstanding performance of semiconductor device 200.

Semiconductor device 200 can also include an interlayer dielectric layeron the top surface of the base layer, where the source region N+ isexposed by the interlayer dielectric layer. Source electrode Source caninclude a first portion that is in contact with the source region N+through the interlayer dielectric layer, and a second portion that is ona surface of the interlayer dielectric layer and extends at least toabove the second conductor. The second portion can be electricallyconnected to the first portion, and may extend from the first portion toabove the second conductor. A portion of source electrode Source can belocated above where the first and second conductors are disconnected.

Semiconductor device 200 can also include a drift region and a bodyregion in the base layer. The drain region can be located in the driftregion, and at least a portion of the withstand voltage layer may belocated on the drift region. The source region can be located in thebody region, and at least a portion of the first dielectric layer may belocated on the body region. The doping type of the body region can bedifferent from the doping type of the source region. For example, anN-type source region can be located in a P-type doped body region Pbodyand may be electrically connected to source electrode Source (shown inFIG. 2 by a connection terminal). The drift region and the drain regionmay have the same doping type. For example, a doping concentration of anN-type drift region N-drift may be less than that of drain region N+,and drain region N+ can be electrically connected to drain electrodeDrain (shown in FIG. 2 by a connection terminal). Body region Pbody mayserve as a channel region of semiconductor device 200, and at least aportion of the first dielectric layer can cover the surface of bodyregion Pbody. A portion of drift region N-drift may be located undervoltage withstanding layer Oxide, and drift region N-drift can extend asfar as possible to body region Pbody in order to hinder lateraldiffusion of body region Pbody toward the drain region.

Referring now to FIG. 3 , shown is a cross-sectional view of a secondexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. One differencebetween semiconductor devices 300 and 200 involves the second conductor.In semiconductor device 300, polysilicon Poly2 may not only be locatedon thick oxide layer Oxide, but also can be located on the firstdielectric layer. For example, polysilicon Poly2 can extend from thesurface of the first dielectric layer to the surface of voltagewithstanding layer Oxide, such that polysilicon Poly2 covers thejuncture region between the first dielectric layer and voltagewithstanding layer Oxide, in order to effectively reduce gate charge Qgdof semiconductor device.

Referring now to FIG. 4 , shown is a cross-sectional view of a thirdexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. One differencebetween semiconductor devices 400 and 200 involves the first conductor.In semiconductor device 400, polysilicon Poly1 may not only be locatedon the first dielectric layer, but also can be located on thick oxidelayer Oxide. For example, polysilicon Poly1 may extend from the firstdielectric layer to thick oxide layer Oxide, such that polysilicon Poly1covers the juncture region between the first dielectric layer andvoltage withstanding layer Oxide, in order to effectively reduce gatecharge Qgd of semiconductor device.

Referring now to FIG. 5 , shown is a cross-sectional view of a fourthexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. Semiconductordevice 500 may differ from semiconductor device 400 in including atleast one third conductor. The third conductor(s) can be located onvoltage withstanding layer Oxide, may be spatially isolated from eachother, and the third conductor adjacent to the second conductor can bespatially isolated from the second conductor. In semiconductor device500, the third conductor layer may be polysilicon Poly3, and each ofpolysilicon Poly3 can be electrically connected to corresponding one ofthe second field plate electrodes. Also, the potential of each of thesecond field plate electrodes may be different from that of first fieldplate Plate1. The closer the polysilicon Poly3 is to the drain regionN+, the higher potential of a second field plate electrically connectedto polysilicon Poly3 is, and the voltage withstanding performance of thedevice can be further improved. In addition, a resistor may be disposedbetween second field plate electrode adjacent to first field plateelectrode, and first field plate electrode Plate1 and/or the resistormay be disposed between the adjacent second field plate electrodes. Forexample, the source electrode may further cover a space between thesecond and third conductors and a space between the third conductor(s).

Referring now to FIG. 6 , shown is a cross-sectional view of a fifthexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. Semiconductordevice 600 is similar to semiconductor device 200, but also can includea reduced surface field effect layer in the base layer, and a lowersurface of the body region and a lower surface of the drift region maynot be lower than an upper surface of the reduced surface field effectlayer. For example, the reduced surface field effect layer can belocated below the body region and the drift region, and the doping typeof the reduced surface field effect layer may be the same as that of thebody region and different from that of the drift region.

The reduced surface field effect layer can assist in depleting the driftregion such that when the drift region has a higher dopingconcentration, it can still be quickly depleted to reduce the surfaceelectric field of semiconductor device 600. Thus, semiconductor device600 may have both low on-resistance (Rdson) and a high breakdown voltage(BV). In order to further reduce on-resistance Rdson of semiconductordevice 600, the first spacing distance between the upper of the reducedsurface field effect layer and the lower surface of the drift region maybe set to be greater than zero. That is, there can be a certain spacebetween the reduced surface field effect layer and the drift region tosupply electrons to flow through. In addition, in order to better adjustthe voltage withstanding characteristic of semiconductor device 600, thefirst spacing distance can be adjusted according to the dopingconcentration of the drift region. For example, the larger the dopingconcentration of the drift region is, the more the auxiliary depletionof the reduced surface field effect layer is needed and the smaller thefirst spacing distance is, and vice versa.

In semiconductor device 600, the reduced surface field effect layer maybe a P-type buried layer PBL formed in N-type high voltage well regionHVNW. In order to provide sufficient dopant of the first type (e.g., thefirst doping type is P-type, and the dopant of first type is P-typedopant) at a position closer to the surface of semiconductor device 600,the second spacing distance between the upper surface of the reducedsurface field effect layer and the lower surface of the body region maybe set to less than or equal to the first spacing distance, in order tobetter assist in deplete the region near the drain region to reduce thesurface electric field of the region. In semiconductor device 600, thelower surface of the body region may be closer to the upper surface ofthe reduced surface field effect layer than the lower surface of thedrift region, body region Pbody can be P-type, and N-type source regionN+ may be located in body region Pbody. Also, the source region can beelectrically connected to source electrode Source (shown as a connectionterminal is illustrated in FIG. 2 ).

In semiconductor device 600, the reduced surface field effect layer canbe a P-type buried layer PBL. In order to ensure that the first spacingdistance is greater than or equal to the second spacing distance, in afirst direction, the junction depth of the drift region may be less thanthe junction depth of the body region, where the first direction refersto a stacking direction of the reduced surface field effect layer andthe drift region. The reduced surface field effect layer insemiconductor device 600 can also be employed in semiconductor devices300, 400, and/or 500.

Referring now to FIG. 7 , shown is a cross-sectional view of a sixthexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. In semiconductordevice 700, the spacing distance between the upper surface of thereduced surface field effect layer (the side close to the drift region)and the top surface of the base layer may not be constant value. Forexample, the third spacing distance between the upper surface of thereduced surface field effect layer located below the body region and thetop surface of the base layer may be less than a fourth spacing betweenthe upper surface of the reduced surface field effect layer locatedbelow the drift region and the top surface of the base layer. Thereduced surface field effect layer located below the body region may beas close as possible to the body region to reduce the surface electricfield, and can improve the breakdown voltage of semiconductor device700. There can be a space between the upper surface of the reducedsurface field effect layer and the lower surface of the drift region, inorder to reduce on-resistance of semiconductor device 700 by thegreatest extent.

In semiconductor device 700, the reduced surface field effect layer maybe composed of first and second buried layers located in the base layer,and the first and second buried layers may be in contact with eachother. At least a portion of the first buried layer can be located belowthe body region, and at least a portion of the second buried layer canbe located below the drift region. A spacing distance between the uppersurface of the first buried layer and the top surface of the base layeris a third spacing distance, and a spacing distance between the uppersurface of the second buried layer and the top surface of the base layeris a fourth spacing distance. The first buried layer can be a P-typeburied layer PBL1, and the second buried layer may be a P-type buriedlayer PBL2. Buried layer PBL1 can be disposed as close as possible toP-type body region Pbody. For example, buried layer PBL1 and P-type bodyregion Pbody can be in direct contact. A voltage of the source electrodeapplied to body region Pbody e.g. the reference ground voltage) may alsobe applied to PBL1 through the body region to avoid dynamic Rdson fromoccurring. Buried layer PBL2 may not be in contact with drift regionN-drift. That is, the first spacing distance can be greater than zero,in order to provide a wider current path for the electrons, and tofurther reduce the Rdson of semiconductor device 700. The reducedsurface field effect layer in semiconductor device 700 can also beemployed in semiconductor devices 300, e 400, and/or 500.

Referring now to FIG. 8 , shown is a cross-sectional view of a seventhexample laterally diffused metal oxide semiconductor device, inaccordance with embodiments of the present invention. In semiconductordevice 800, an isolation layer can be located in the base layer andbelow the reduced surface field effect layer. The isolation layer mayisolate the reduced surface field effect layer from the bottom portionof the base layer to facilitate high voltage application ofsemiconductor device 800. In this particular example, the isolationlayer may be third buried layer NBL of the N-type doped located in highvoltage well HVNW and can be located below buried layer PBL. Also, thedoping concentration of the third buried layer NBL may be heavier thanthat of the high voltage well HVNW. Similarly, the isolation layerdescribed in semiconductor device 800 may be employed and disposed belowthe reduced surface field effect layer in semiconductor device 700.

In particular embodiments, a method of manufacturing a laterallydiffused metal oxide semiconductor device, can include forming a sourceregion and a drain region in a base layer, and forming a firstdielectric layer on a top surface of the base layer, where the firstdielectric layer is adjacent to the source region. The method can alsoinclude forming a voltage withstanding layer between the firstdielectric layer and the drain region, forming a conductor layer on thefirst dielectric layer and the voltage withstanding layer, and forming afirst conductor at least partially located on the first dielectric layerand a second conductor at least partially located on voltagewithstanding layer by etching the conductor layer. The first and secondconductors can be spatially isolated. The method can also includeforming a source electrode electrically connected to the source region,where the source electrode at least covers a space between the first andsecond conductors. Before forming the source electrode, an interlayerdielectric layer can be formed on the top surface of the base layer. Thesource region may be exposed by the interlayer dielectric layer. Thesource electrode can include a first portion in contact with the sourceregion through the interlayer dielectric layer, and a second portionlocated on a surface of the interlayer dielectric layer and extending atleast to above the second conductor.

In particular embodiments, a semiconductor device can be formedaccording to the example manufacturing method, as shown in FIGS. 2-8 .High voltage well region HVNW can be formed in semiconductor substratePSUB, and base layer can include high voltage well region HVNW andsemiconductor substrate PSUB. A field oxide layer may then be formedusing a local oxidation of silicon (LOCOS) process. Voltage withstandinglayer Oxide can be formed using the LOCOS process after limiting thehigh-voltage drain region with a mask, and the drift region and thereduced surface field effect layer can be formed.

Further, after forming the reduced surface field effect layer, themethod can also include forming an isolation layer (e.g., an NBL layer)in the base layer. The isolation layer can be located below the reducedsurface the field effect layer in order to isolate the reduced surfacefield effect layer from the bottom portion of the base layer. Inparticular embodiments, a method of manufacturing a semiconductor devicecan also include forming a first dielectric layer as shown in FIGS. 2-8. That is, a gate dielectric layer, and then a conductor layer (e.g., apolysilicon layer) may be deposited on the first dielectric layer andvoltage withstanding layer Oxide, and the deposited conductor layer maybe etched to form the first, second, and third conductors, as shown inFIGS. 2-8 .

The first dielectric layer may be adjacent to the source region. Afterforming the first and second conductors, the method can include forminga body region (e.g., a P-type body region), as shown in each of FIGS.2-8 . A lightly doped drain (LDD) region (e.g., an n-type lightly doped[NLDD] region) can be formed in the body region (e.g., Pbody) and thedrift region by an ion implanting process. The second spacing distancebetween the body region and the reduced surface field effect layer maybe less than or equal to the first spacing distance. After forming thebody region and the lightly doped region, sidewalls spacers can also beformed at the side surfaces of the first, second, and/or thirdconductors, that are shown in FIGS. 2-8 . In addition, a source regionand a drain region may respectively be formed in the body region and thedrift region. Further, a source electrode, a drain electrode, a gateelectrode, and field plate electrodes can also formed, where the sourceelectrode may extend at least to above the second conductor.

In addition, when forming the reduced surface field effect layer, thefirst spacing distance may be adjusted according to the dopingconcentration of the drift region. For example, the higher the dopingconcentration of the drift region, the smaller the first spacingdistance. A reduced surface field effect layer having two P-type buriedlayers (see, e.g., FIG. 3 ) may also be formed by using two masks. Athird spacing distance between the upper surface of the reduced surfacefield effect layer located below the body region and the top surface ofthe base layer can be less than a fourth spacing distance between theupper surface of the reduced surface field effect layer located belowthe drift region and the top surface of the base layer.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with modifications as are suited to particularuse(s) contemplated. It is intended that the scope of the invention bedefined by the claims appended hereto and their equivalents.

What is claimed is:
 1. A method of manufacturing a laterally diffusedmetal oxide semiconductor device, the method comprising: a) forming asource region and a drain region in a base layer; b) forming a firstdielectric layer on a top surface of the base layer, wherein the firstdielectric layer is adjacent to the source region; c) forming a voltagewithstanding layer between the first dielectric layer and the drainregion; d) forming a conductor layer on the first dielectric layer andthe voltage withstanding layer; e) forming a first conductor at leastpartially located on the first dielectric layer, a second conductor atleast partially located on the voltage withstanding layer, and aplurality of third conductors that are spatially isolated and located onthe voltage withstanding layer, by etching the conductor layer; f)forming a gate electrode electrically connected to the first conductorand a first field plate electrode electrically connected to the secondconductor; and g) forming a source electrode electrically connected tothe source region, h) wherein the first and second conductors arespatially isolated, and the source electrode at least covers a spacebetween the first and second conductors and a space between the secondconductor and an adjacent one of the plurality of third conductors. 2.The method according to claim 1, wherein before the forming the sourceelectrode, further comprising forming an interlayer dielectric layer onthe top surface of the base layer, wherein the source region is exposedby the interlayer dielectric layer, the source electrode comprises afirst portion in contact with the source region through the interlayerdielectric layer, and a second portion located on a surface of theinterlayer dielectric layer and extending at least to above the secondconductor.
 3. The method according to claim 1, wherein the first fieldplate electrode and the source electrode are coupled to the samepotential.
 4. The method according to claim 1, further comprisingforming a plurality of second field plate electrodes that each areelectrically connected to a corresponding one of the plurality of thirdconductors, wherein a potential of a second field plate electrode thatis closer to the drain region is higher than a potential of a secondfield plate electrode that is farther from the drain region.
 5. Themethod according to claim 1, further comprising forming a drift region,a body region, and a reduced surface field effect layer in the baselayer, wherein: a) the drain region is located in the drift region, andat least a portion of the voltage withstanding layer is located on thedrift region; b) the source region is located in the body region, and atleast a portion of the first dielectric layer is located on the bodyregion; c) a lower surface of the body region and a lower surface of thedrift region are not lower than a upper surface of the reduced surfacefield effect layer; and d) a doping type of the reduced surface fieldeffect layer is the same as that of the body region and have differentfrom that of the drift region.
 6. The method according to claim 5,further comprising forming an isolation layer below the reduced surfacefield effect layer, wherein the reduced surface field effect layer and abottom portion of base layer are isolated by the isolation layer.
 7. Themethod according to claim 1, wherein the source electrode further coversspaces between each of the plurality of third conductors.
 8. The methodaccording to claim 1, wherein a juncture region between the firstdielectric layer and the voltage withstanding layer is covered by one ofthe first conductor and the second conductor.
 9. The method according toclaim 5, wherein a first distance between the reduced surface fieldeffect layer and the drift region is greater than zero.
 10. The methodaccording to claim 9, wherein a second distance between the reducedsurface field effect layer and the body region is less than or equal tothe first distance.
 11. The method according to claim 5, wherein thegreater the doping concentration of the drift region, the smaller thefirst distance.